The invention relates to an apparatus for the monitoring of groundwater for environmental investigations. More specifically, the invention is a horizontal advanced tensiometer which measures the xe2x80x9csoil water potentialxe2x80x9d (how well surrounding soil and rock hold water) of soil and rock positions beneath objects or overlying material.
Since soil water potential indicates how well surrounding soil and rock holds water, measuring soil water potentials at various locations and depths allows scientists to understand how fluids move between the land surface and the water table below. Understanding how fluids travel through the soil is an important aspect of environmental studies and is very helpful in developing improved irrigation management. Traditionally, tensiometers have been the instruments of choice for recording such water potential measurements.
Traditional tensiometers consist of a sealed tube (filled with water) which is connected to a hollow porous tip at one end and a vacuum gauge at the other. The porous tip is then inserted into the soil at the desired monitoring position. As the water content of the surrounding soil decreases so does its water potential relative to that of the water in the tip. The difference in water potential causes the water in the sealed tube to move through the tip pores and into the surrounding soil. Thus, relatively dry soil pulls water through the porous tip and creates a partial vacuum in the tube. The vacuum gauge then records the pressure level of the ambient soil. The more saturated the soil, the less vacuum created, and the lower the pressure recorded.
Many of the problems associated with traditional tensiometers were solved with the development of advanced tensiometers. Advanced tensiometers utilize electronic pressure transducers mounted at the point of measurement which eliminate the need for the long water columns taught by traditional tensiometer designs. See, Hubbell et al., U.S. Pat. No. 5,915,476.
Although advanced tensiometer designs have solved the problem of water column length, previous tensiometer designs have failed to solve problems associated with monitoring soil conditions in areas beneath objects or material. Previous tensiometer designs have difficulty in measuring such areas because they employ vertical monitoring wells that are inefficient or ineffective in monitoring soil which lies beneath buildings or other structures or material.
There remains a need for horizontal monitoring of soil moisture potentials in areas beneath objects where vertical monitoring devices would be inefficient or ineffective.
An object of the invention is to provide an apparatus to measure soil water potential beneath the earth""s surface.
Another object of the invention is to provide an apparatus to measure soil water potential in horizontal layers beneath objects or overlying material.
Another object of the invention is to provide a means of maintaining the seal between the transducer and the adapter to ensure accurate measurements.